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A fibrous white mineral composed of calcium metasilicate. Wollastonite was named for the English mineralogist William Wollaston in the early 1800s. The mineral is formed by the metamorphosis of siliceous limestones at high temperatures (>600 C). Major sources of wollastonite occur in Romania (Ciclova Romîna), Finland (Pargas), Mexico, the U.S. (Utah, Michigan, California, New York) and Italy (the lavas of Monte Somma and Vesuvius). Wollastonite is used in ceramics, floor tiles, insulators, paints, plastics, and cements. It has also been used as a bubble-free white opacifier in glazes. Wollastonite can form as a decomposition product during glass devitrification.



Synonyms and Related Terms

tabular spar; calcium silicate


  • Inhalation and contact may cause skin, eye and lung irritation.

Physical and Chemical Properties

  • Triclinic system with tabular crystals, fibers or masses.
  • Perfect cleavage in two directions.
  • Fluorescent. May be white, gray, yellow, red or brown.
  • Fracture = uneven or splintery.
  • Luster = vitreous to silky.
  • Streak = white
Composition CaSiO3
Mohs Hardness 4.5 - 5.5
Density 2.8-3.1 g/ml
Refractive Index 1.62 - 1.65

Resources and Citations

  • G.S.Brady, Materials Handbook, McGraw-Hill Book Co., New York, 1971 Comment: p. 133
  • Susan E. Schur, Conservation Terminology: A review of Past & Current Nomenclature of Materials, Technology and Conservation, Spring (p.34-39); Summer (p.35-38); Fall (p.25-36), 1985
  • Michael McCann, Artist Beware, Watson-Guptill Publications, New York City, 1979
  • Robert Fournier, Illustrated Dictionary of Practical Pottery, Chilton Book Company, Radnor, PA, 1992
  • C.W.Chesterman, K.E.Lowe, Audubon Society Field Guide to North American Rocks and Minerals, Alfred A. Knopf, New York, 1979
  • Random House, Webster's Encyclopedic Unabridged Dictionary of the English Language, Grammercy Book, New York, 1997
  • The American Heritage Dictionary or Encarta, via Microsoft Bookshelf 98, Microsoft Corp., 1998